1. Field of the Invention
The present invention relates to a device and method for reducing the temperature of a bombe in a liquefied petroleum gas (LPG) vehicle. More particularly, it relates to a device for reducing the temperature of a bombe using the fact that LPG absorbs latent heat during vaporization to ensure smooth LPG filling, and a control method thereof.
2. Description of Related Art
Typically, an LPG vehicle is refueled at a filling station as shown in FIG. 1. An LPG storage 1 is located in the underground of the filling station, and the fuel is pumped by a filling pump 2 and transferred to each filling device. The filling device includes a filling gun 3 for supplying fuel to a fuel inlet of the vehicle, and a bombe 10 for storing fuel is mounted in the vehicle.
Here, the pressure at the filling state should be higher than that of the bombe 10 mounted in the vehicle such that the fuel injection and filling through the filling gun 3 is made possible. The pressure at the filling station may be determined as a sum of the pressure of the LPG storage 1 and the performance (about 8 bar) of the filling pump 2.
In the case of a vehicle using an existing liquid phase injection (LPI) system, the pressure at the filling station becomes lower than or equal to the pressure of the bombe 10 in the vehicle, and thus the LPG filling is not achieved. In particular, the temperature during a hot summer in Europe is 40° C., and the content of propane in LPG is 25 to 95%. Moreover, the temperature during a hot summer in Australia is 50° C., and the content of propane in LPG is 50 to 100%, for example. Thus, the pressure in the bombe 10 excessively increases under such conditions.
The increase in pressure of the bombe 10 of the vehicle causes an increase in temperature of the bombe 10, and this increase in temperature of the bombe 10 is caused by a fuel return system of an LPI engine as shown FIG. 2. FIG. 2 is a schematic diagram showing a fuel circulation system in a conventional LPI system.
In the LPI system, LPG is injected from a filling gun 3 provided with a nozzle into a bombe 10 through an LPG filter and an over-current protection (OCP) valve. The high-pressure liquid phase fuel in the bombe 10 is supplied to an engine through a fuel supply line, and extra fuel and fuel heated by the engine are reintroduced into the bombe 10 through a fuel return line. Here, the temperature in the bombe 10 is increased by the heated fuel to vaporize the liquid fuel, and thus the internal pressure of the bombe 10 also increases. As such, the increase in pressure of the bombe 10 may cause the problem of poor filling in the vehicle employing the LPI system.
In order to solve such a problem and ensure smooth LPG filling, it is necessary to substantially reduce the temperature of the bombe 10 by more than 25° C. or increase the pressure at the filling station by more than 6.1 bar. Conventional methods generally include a method of minimizing the flow of return fuel and a cooling method of reducing the temperature of the return fuel by heat exchange.
However, in the case of the method of minimizing the flow of return fuel by installing a solenoid valve in the fuel return line, the pressure at an injector excessively increases, and the startability and operability deteriorate. Moreover, in the case of a method using a system in which the return fuel is completely eliminated, it is impossible to collect fuel remaining in the injector after starting off, which causes injector leakage due to fuel vaporization, and the startability and operability also deteriorate.
Further, in the cooling method of reducing the temperature of the return fuel by heat exchange, in the case of a method of exchanging heat with air conditioner coolant, which is disclosed in Korean Patent No. 10-1071236, it is necessary to forcibly drive an air conditioner at a predetermined fuel temperature, which reduces the fuel efficiency and competitiveness, increases the manufacturing cost, and reduces the efficiency of the air conditioner. Moreover, in the case of a method of exchanging heat with other fluids such as condensed water, air, etc., there is no significant effect of reducing the temperature.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.